Begin by making the breadcrumbs. Warm the olive oil in a medium skillet, then add the garlic and chopped sage. Cook for one minute, then add the breadcrumbs and salt. Cook the breadcrumb mixture for a few minutes, stirring, until they are golden brown. Remove from the heat and transfer to a small bowl. Set aside until later.

Bring a large pot of water to a boil for the pasta. Season the water generously with salt, then cover the pot and turn down the heat to low. Keep it warm so that it’s ready to cook the pasta later.

Use a box grater or a food processor with the shredding attachment to shred the onion. Melt the butter in a large dutch oven or stock pot over medium heat, and add the shredded onion and ½ teaspoon of the salt. Cook, stirring occasionally, until softened, about 20 minutes. Adjust the heat to a lower setting, if needed, to avoid browning.

While the onion cooks, shred the apple as well.

Pour the crushed tomatoes into the pot along with the teaspoon of sugar. Bring to a low simmer, then stir in the shredded apples and remaining teaspoon of salt. Cook, stirring occasionally, for about 20 minutes. You can partially cover the pot to keep it from splattering.

While the sauce is cooking, make the pasta. You’ll want to time this so the sauce is finished cooking before the pasta is. If you aren’t quite sure, err on the side of starting the pasta later. You can always keep the sauce over very low heat while the pasta cooks, as it is hard to overcook this sauce. Bring the water in the pot back to a boil and add the spaghetti. Cook until the pasta is al dente, then use tongs to transfer it directly into the pot with the sauce. Stir to coat, adding a little pasta water if the mixture seems too thick. Remove from the heat and stir in the cheese, then taste for seasoning. Add more salt if necessary.

To serve, transfer the pasta to a bowl and top with the breadcrumbs passing more grated cheese if you like.